IMMUNOLOGICAL MECHANISMS OF DESENSITIZATI ON

The immunological mechanisms underlying the efficacy of specific desen sitization have been the subject of many studies. Various modification s have been observed, such as a fall in specific IgE, a rise in IgG bl ocking antibodies, a fall in effector cell reactivity affecting mast c ells, basophils and eosinophils. The role of suppressor lymphocyte reg ulatory cells has also been demonstrated. None of these modifications, on its own, is able to explain the mechanisms of action of desensitiz ation. The recent demonstration that desensitization is able to change Th-2 polarization observed in allergic reactions to a Th-1 type profi le has allowed previous observations to be combined into a single conc ept. The reduction of IL-4 appears to prevent the isotypic switch to I gE and promotes the production of IgG. The anergy of Th-2 cells would induce a reduction of mast cell and eosinophil reactivity. The inducti on of type 1 allergen-specific cells, especially CD8(+), producing IFN -gamma, would account for the previously reported suppressor effects. However, the precise mechanisms of this change of polarization are unk nown, and the correlation with clinical efficacy has yet to be evaluat ed.